A construction machinery, such as a crane, includes an operating device configured to remote-control a boom actuator, a bucket actuator, or the like via a main hydraulic switching valve. The operating device includes a tiltable lever and controls the amount of oil supplied to the actuator in accordance with a tilt amount of the lever. In many cases, a plurality of operating devices are provided at the construction machinery so as to be coupled to one another, and in some cases, the plurality of operating devices are operated at the same time. In such a case, the lever is required to be temporarily held at an intermediate position where the lever is tilted from a neutral position by a predetermined tilt amount, or at a stroke end. To realize this, the operating device includes a detent mechanism configured to temporarily fix the lever at the intermediate position or the stroke end. Examples of the detent mechanism include a mechanical detent mechanism described in PTL 1 and an electromagnetic detent mechanism described in PTL 2.
The mechanical detent mechanism described in PTL 1 includes a cam disc configured to rotate together with a lever, and a steel ball is pressed against an outer peripheral surface of the cam disc by a detent spring. When the lever is tilted, the steel ball is displaced relative to the cam disc along the outer peripheral surface of the cam disc. A step is formed on the outer peripheral surface of the cam disc. When the lever is further tilted, the steel ball falls down along the step. When returning the tilted lever back in a neutral direction after the steel ball has fallen down from the step, the fallen steel ball hits the step. Since the steel ball is pressed against the outer peripheral surface of the cam disc by the detent spring, the steel ball engages with the step to inhibit the cam disc from returning in cooperation with the step, that is, the steel ball detents the cam disc. When a cancel torque is applied to the detented cam disc in a direction toward the neutral position, the detent state of the cam disc is canceled. The adjustment of the cancel torque necessary to cancel the detent state can be performed by adjusting a pressing margin of the detent spring.
PTL 2 describes first and second electromagnetic detent mechanisms. The first electromagnetic detent mechanism of an operating device includes an electromagnetic adsorption mechanism and a detent plate. The electromagnetic adsorption mechanism includes a detent pin, and a coil plate is attached to the detent pin. The electromagnetic adsorption mechanism includes a magnetic coil provided so as to surround the detent pin. When a current is supplied to the magnetic coil, the coil plate is attracted by the magnetic coil to restrict the downward movement of the projecting detent pin by a certain force. The detent plate moves in a left-right direction integrally with the lever. When the lever is tilted to move the detent plate to a predetermined intermediate position, the projecting detent pin engages with the detent plate. With this engagement, the detent plate is detented at the intermediate position. The detent state of the detent plate is canceled by the application of the cancel torque in the direction toward the neutral position. The cancel torque necessary to cancel the detent state can be adjusted in accordance with the current supplied to the electromagnetic adsorption mechanism.
The electromagnetic adsorption mechanism is provided with a spring configured to bias the coil plate toward the magnetic coil. Even in a case where the detent pin is pushed back when canceling the detent state, an interval between the coil plate and the magnetic coil can be favorably maintained by the spring.
The electromagnetic adsorption mechanisms configured as above are respectively provided at both left and right sides of the detent plate. Therefore, even in a case where the detent plate moves to the left or right, the electromagnetic adsorption mechanism can detent the detent plate.
In an operating device including the second electromagnetic detent mechanism described in PTL 2, an operating rod moves in accordance with the tilting of the lever to bias a valve element (such as a spool). The detent mechanism is provided with an electromagnetic adsorption mechanism and a friction detent member. The electromagnetic adsorption mechanism is similar in configuration to the electromagnetic adsorption mechanism adopted in the first electromagnetic detent mechanism, and a detent member is provided at a tip end of the electromagnetic adsorption mechanism. The friction detent member is provided such that the operating rod is inserted therethrough. When a current is supplied to the electromagnetic adsorption mechanism, the friction detent member is pressed against the operating rod. Thus, the operating rod can be detented at an arbitrary position. When the supply of the current to the electromagnetic adsorption mechanism is stopped, the friction detent member is separated from the operating rod. Thus, the detent state is canceled.
As with the above, in the second electromagnetic detent configured as above, the electromagnetic adsorption mechanisms are respectively provided at both left and right sides of the lever. Each electromagnetic adsorption mechanism is provided with one operating rod. With this, even in a case where the lever is tilted to the left or right, the lever is detented.